Flow noise suppression system for a sonar dome

Abstract

Apparatus for suppression of water flow noises in connection with a keel nted sonar dome. A solution of water soluble polymer is ejected through a series of holes along the leading edge of the sonar dome under forward movement of the ship. The concentration and flow rate is chosen to "bathe" the dome in a very dilute dispersion (of the order of 10 parts per million by weight) of the polymer.

I claim: 
     
       1. In a sonar transducer unit adapted to be carried by a moving water vehicle external to the hull thereof and submerged in the ambient stream, the combination comprising; (a) an acoustically transparent shell forming a substantially closed container about the transducer unit, and   (b) means for injecting a dilute aqueous solution of a water soluble polymer material of a first predetermined concentration into the layer of ambient water flow adjoining the exterior of the surface of the shell in such a manner that substantially the entire exterior surface of the shell is bathed in the sheath of dispersed solution.   
     
     
       2. Apparatus in accordance with claim 1, wherein; (c) said water soluble polymer material is further of a type having a molecular weight in excess of 1,000,000 and having a long chain, linear, molecular structure.   
     
     
       3. Apparatus in accordance with claim 1; (d) said aqueous polymer solution being injected into the layer of ambient water flow at a flow rate chosen to maintain a concentration of polymer material of at least 10 parts per million by weight in said sheath at all regions along the surface of the shell.   
     
     
       4. Apparatus in accordance with claim 1 of the type adapted to be keel mounted to a surface ship, (e) said shell having a hydrodynamically streamlined shape symmetric about a plane parallel to the keel line of the ship, and   (f) said means for injecting comprises a row of ejection orifices along the leading edge of the container.   
     
     
       5. Apparatus in accordance with claim 4 wherein; (g) the shell forms a chin portion where its leading edge merges with the bottom surface thereof, said row of ejection orifices extending around said chin portion.